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Monday, 13 August 2012

a. Amplification.

The transistor may be used as a current, voltage, or power amplifier. For instance, a stronger signal current, may be obtained from a transistor than is fed into it. A signal of 1 milliampere fed into the input circuit of the transistor may appear as 20 milliamperes at its output. Various circuit arrangements provide for various amounts of signal amplification.

b. Oscillation.

The transistor may be used to convert direct-current energy into alternating-current energy ; that is, it may be used as an oscillator. When functioning in this manner, the transistor draws energy from a dc source and, in conjunction with a suitable circuit arrangement, generates an ac voltage .

c. Modulation and Demodulation.

The transistor used in various circuit arrangements can provide amplitude modulation (variation in amplitude of an rf signal) or frequency modulation (variation in frequency of an rf signal). Demodulation (detection) of amplitude-modulated signals or frequency modulated signal may be accomplished with transistors. These circuits are well-suited for miniature transmitters intended for short range applications.

d. Miscellaneous.

The transistor may also be used to modify the shape of signal wave forms. Wave form shaping is vital in various types of radar, teletypewriter, computer, and television circuits. A indicates the use of the transistor in transforming a sine wave into a square wave. indicates the use of the transistor in clipping the negative alterna-tions of a series of positive and negative pulses.

e. Switching

This is the main application of Transistors in many areas ,when transistor used as an electronic switch , a transistor is normally operated alternately in cutoff and saturation region. Digital circuits make use of switching characteristics of transistor.